1. Field of the Invention
The present invention relates to a steering angle neutral position detection error protecting method for a method for detecting a steering angle neutral position based on a difference in velocity between right and left driven wheels of a vehicle and a detection error protecting apparatus for an apparatus for detecting that neutral position.
2. Description of Related Art
Conventionally, in a steering unit of the vehicle, an electronic control unit (ECU) of the steering unit computes a necessary steering angle and the like based on steering angle information or vehicle velocity transmitted from a vehicle mounted ECU which processes an output signal of a steering angle sensor in order to know a neutral position of the steering angle by a steering wheel.
However, there may occur a timing in which the ECU cannot send steering angle information and the like when the ECU which has a job of transmitting the steering angle information and the like is stopped or just after the vehicle engine is started. Thus, the neutral position of the steering angle cannot be known at that timing. For the reason, a wheel velocity of the driven wheel is detected and the neutral position of the steering angle is detected based thereon. That is, because if the steering angle is not located at the neutral position, a difference in velocity between the right and left vehicle driven wheels is generated, the neutral position of the steering angle is detected by detecting whether or not there is a difference in velocity between the right and left vehicle driven wheels.
As described above, according to the method for detecting the neutral position of the steering angle, whether or not the difference in velocity between the right and left vehicle driven wheels exists is determined based on an output signal from a vehicle wheel velocity sensor which detects the wheel velocity of each of right and left driven wheels. However, it can be considered that the signal outputs of the right and left vehicle wheel sensors turn to the same value due to, for example, short-circuit of a signal output circuit or a short-circuit of a signal line or the like. In such a case, it is detected as if the steering angle is located at the neutral position although the difference in velocity between the right and left driven wheels exists. Thus, a steering unit which controls the steering using such sensor signals or a vehicle operation control unit has a problem that its appropriate control may be disturbed.